Sunday, December 30, 2012

We have known since 1962 (thanks to Mariner II) that Venus does not possess a magnetic field of its own (Sonett 1963). In the late 1970's, the Pioneer Venus Orbiter's magnetometer detected large-scale, steady magnetic fields in the Venusian ionosphere during solar maximum, when the solar wind dynamic pressure was great enough to overcome the ionosphere's thermal pressure. These magnetic fields are mainly oriented horizontally, and often exceed 100 gammas (Luhmann et al. 1980).

Even when the ionosphere was not dominated by the solar wind, the Pioneer craft detected small-scale magnetic features interpreted as flux ropes, structures that resemble a helix of woven magnetic fields, not unlike a rope. This led researchers to conclude that the ionosphere's magnetic state could be categorized in two forms: magnetized, and unmagnetized with some small-scale flux ropes (Luhmann et al. 1980).

A recent publication aims to change this long-standing picture of the Venusian ionosphere, as a result of observations made by the Venus Express spacecraft since its orbit was modified such that it now reaches periapsis at a latitude of 90 degrees (over the North pole) and a height above Venus of only 170 km (well into the ionosphere).

T. L. Zhang and colleagues (2012) report that during solar minimum, Venus Express observed "giant flux ropes" embedded within a magnetized ionosphere. They determined these woven structures to be on the order of 100 kilometers in diameter, 10 times the size of the flux ropes detected by Pioneer in an unmagentized ionosphere. The magnetic flux contained within the giants ropes measures near 1000 Webers, much greater than the 2 to 3 Weber fluxes in the small ropes.

It is notable that in over 100 orbits when the Venus Express magnetometer detected these enhanced magnetic strength structures, they detected only one such giant rope during passage through periapsis. In addition, while the giant rope structure is seen as a single event by Venus Express only near 90 degrees latitude, the small flux ropes observed by Pioneer occurred throughout the dayside atmosphere.

These researchers propose that the Venusian ionosphere has a third known state, in addition to the two mentioned above (Zhang et al. 2012). The possible states are:

Magnetized (during solar maximum and high solar wind pressure)

Unmagnetized with small-scale flux ropes (during solar minimum)

Magnetized with embedded giant flux ropes (during solar minimum)

And what do they believe is the cause of these large-scale magnetic helixes? It remains "unknown and speculative."

It is interesting that Venus is not the only rocky planetary body in our solar system to display magnetic flux ropes. The Mars Global Surveyor spacecraft has detected flux ropes in the ionosphere of Mars, and Cassini has detected twisted magnetic fields in the lower ionosphere of Titan that resemble the flux ropes observed on Venus and Mars (Wei et al. 2010).

Thursday, December 20, 2012

Are you a planetary scientist studying the Venusian atmosphere, or an engineer looking to build spacecraft or instrumentation that will further the study of our twin planet? Then clear your calendar on January 24th, 2013.

NASA's Glenn Research Center, along with the Ohio Aerospace Institute, is sponsoring a Science and Technical Interchange Meeting (STIM) on the topic of Venus Upper Atmosphere Investigations.

The aim of this day-long set of meetings is to encourage the discussion of shared goals and priorities with regard to the study of the atmosphere of Venus by spacecraft.

discuss spacecraft concepts and technologies that could reach the Venus UA and collect and return the desired data.

If you cannot attend in person, they may be making arrangements for attending remotely-- I have a question out to one of the organizers and I'll update this post accordingly.

If you are lucky enough to be able to travel to the workshop and can arrive a day early, they are planning a tour of the nearly-completed NASA Glenn Extreme Environments Rig (GEER) on the afternoon of the 23rd. Once completed, the GEER will be able to accurately simulate any planetary environment in the solar system, including both the surface and the atmosphere of Venus. Read more about the GRC's Strategic Science work here.

Thursday, November 29, 2012

While one Soviet Venera spacecraft certainly passed near Venus prior to August of 1962, it was not successful in transmitting any data back to Earth... so Mariner II gets the credit for being the first successful probe to visit Venus.

Launched on August 27, 1962, Mariner II carried the following experiments intended for use at Venus (other instruments also took measurements of interplanetary space while enroute):

Microwave radiometer - meant to determine the temperature of the planet's surface and details concerning the atmosphere.

Infrared radiometer - meant to determine the structure of the cloud layer, and temperature distributions at cloud altitudes.

Magnetometer - meant to detect Venus' magnetic field

Mariner II arrived at its encounter point on December 14, almost four months after launch. Never intended to enter orbit or plunge into the Venusian clouds, the spacecraft began recording as much information as it could in the short time Venus would be in range (the spacecraft was moving at 6.743 km/s relative to Venus). A special command from Earth placed Mariner II in "encounter" mode, during which it transmitted all recorded data in real time. It passe within 34,854 km, and seven hours later, Mariner II returned to cruise mode to continue on in a heliocentric orbit. Communication was lost on January 3, 1963.

So what did we learn about Venus from Mariner II?

The 19-mm microwave radiometer indicated roughly equal temperatures on the light and dark sides of the planet:

dark side = 460° K

terminator = 570° K

light side = 400° K

Near Venus, there was no indication of a magnetic field or of appreciable change in the solar plasma flux or the charged particle flux.

The infrared radiometer measured atmospheric temperatures that are consistent with Earth-based observations (hovering around 230° K), and detected no significant difference between the light and dark sides of the planet.

Mass of Venus: 4.87 x 10^24 kg (0.81485 of Earth)

Mariner II was successful by any measure, and set the stage for continued exploration of the inner solar system. It was followed to Venus by a number of probes from the U.S., the Soviet Union, and the European Space Agency. More to come!

Thursday, November 15, 2012

Earlier this week, news outlets and Twitter were abuzz with recent news of a "rogue" and "orphaned" planet detected "wandering" through space a mere 100 light years from us. I found this kind of reporting somewhat misleading, since it conjured images of a planet that was somehow flung out of orbit around its parent star, now left all alone in the cold... wandering... and even though the BBC article did a pretty good job of conveying some of the scientific conclusions, they still used quotes from the study's authors that sensationalized the "homeless planet" idea.

Philippe Delorme and his colleagues begin their report by questioning the dividing line between planets and star-like objects. Currently, the Astronomical Union defines a planetary mass as one falling below the necessary minimum for thermonuclear fusion of deuterium (roughly 13 Jupiter masses), with brown dwarfs and stars above that line. And while this new object weighs in far below that mass boundary and physically meets this criterion for a planet, there's more to the story. It seems CFBDSIR2149 is tagging along with 30 or so young stars (similar in both age and composition) known as the AB Doradus Moving Group (ABDMG). This association means it is likely about the same age and that it formed under similar circumstances. For this reason, Delorme, et al. speculate that CFBDSIR2149 is an object resulting from stellar formation processes. And even though its mass is insufficient to burn deuterium, it should not be classified as a planet.

What they think they know: CFBDSIR2149 is a free-floating substellar object with a mass of 4-7 Jupiter masses, a surface tempurature of ~700K, and is likely a member of the AB Doradus group of stars that are between 50 ans 120 million years old.

Fun facts:

CFBDSIR stands for Canada-France Brown Dwarf Survey InfraRed

The authors find the probability that CFBDSIR2149 is a member of the ABDMG is 87%

They are continuing their parallax measurements of CFBDSIR2149 to confirm or deny its membership in the AB Doradus group (no doubt another paper will be forthcoming)

Tuesday, November 6, 2012

Have you read about AcWriMo? Yep, its a sort of National Novel Writing Month (NaNoWriMo) for academic writing. I've decided to participate, and yes, I'm a little late to the game (It's already November 6).

This is where I make set a crazy goal: Complete a publishable (format and content, anyway) literature review of current thinking on astrobiological possibilities (past and present) for Venus by November 30.

Go Public: I just did with this blog post!

Strategy: Well, it's like writing anything, so there is a sequence for me:

Collection: Find the published papers I will start with for the research. This entails a lot of time with Google Scholar, RefWorks, and the SAO/NASA Astrophysics Data System.

Reading. just what it says, plus note-taking.

Organization: Taking all of my notes and organizing them into the sections of the paper

Writing.

There is a fair amount of rinse & repeat between steps 1 and 2, since good papers will lead me to others. Even so, there is something to be written every day, almost from the beginning.

Mars is getting a lot of attention lately. Truth be told, Mars has been getting a lot attention for quite some time: landers, rovers, orbiters, and Elon Musk and President Obama want to send people there. Mars One is creating a reality TV show to send contestants to the surface of Mars!

So what about Earth's "sister" planet? Where's the love for Venus? [This question is all the more ironic given that in Roman mythology, Venus was the goddess of love, beauty, sex, and all that.]

Well, I am not going to sit idly and do nothing. I'm going to start giving Venus more of the attention it sorely deserves! Here are some of my reasons:

Venus is right there every night (well, most nights)! It's the second-brightest object in the night sky, and its phases can be observed with binoculars.

It is the closest-approaching planet to Earth (38 million kilometers at its closest)

It is roughly the same size and mass as Earth

It has an honest-to-goodness atmosphere

It possesses the most similar environment to Earth conditions in the solar system1

It may have harbored life in its early days

I've been interested in Venus for quite some time, and have always wanted to dig a little deeper into the subject. Be careful what you wish for! I'm currently taking a UND grad course in Astrobiology, and our final assignment is to write a literature review on an astrobiological subject. I chose Venus, so it's going to be all Venus, all the time for me.

I'll do what I can to share interesting snippets here on the blog as I go, but I also plan to write some topical articles such as:

Robotic Missions to Venus: Past, Present

Robotic Missions to Venus: Proposed

The Case for Human Missions to Venus

Venus Facts You Should Know

Check back, I'll try to keep the material coming every week or so for a while.

Footnotes

1. This is not at the surface... it is about 50km up into the Venusian atmosphere.

Friday, October 26, 2012

I've read a lot of articles lately (or at least I've seen their headlines) lamenting the fragmented way many people now consume information. It seems everyone who is "connected" via social media splinters their time so much that they are unable to do a deep dive on anything, failing to learn something beyond a soundbite of information.

I have personal experience with this problem. A few years ago, I discovered RSS, and began constructing an intimidating list of bloggers and journalists that I wanted to follow. Like everyone else, I was unable to keep up. The number of back-logged readings grew to the point that I was incapable of clicking on my favorite feeds because I knew I could not possibly read through even a small fraction of the hundreds of articles still marked as "unread."

More recently, I created a twitter account and began following three or four hundred astronomers, space program writers, and space enthusiasts. Of course, unless you sit with a Twitter window open and continuously scan these tasty morsels, you're gonna miss something. And when I do follow a link to an interesting bit of longer-form writing, I don't have the time to read it. Off it goes to my Instapaper account, where it sits forever unread (for much the same reason).

What is the state of my writing now? The metaphorical fields of my blogs lie fallow, and all I make time for is tweeting (or re-tweeting) interesting original work by others, much of which I have not read in its entirety (see earlier remarks). Not only am I no longer capable of dedicating time to reading longer works, I'm also unable to dedicate time to creating anything exceeding a sentence in length.

The internet and social media have created attention-deficit symptoms that I never experienced before, a malady I've come to believe might only be cured by a 28-day program that excludes all information sources, save possibly a daily newspaper.

I feel I might also benefit from a similar approach with regard to writing: Allow myself to only create written work that exceeds some arbitrary word count significantly longer than a tweet or a Facebook post. Naturally I want to be clever about it, so I set about picking a number that tied to some familiar idea, and that was very Mama Bear-like in size. The very familiar adage "a picture is worth a thousand words" appealed to me, but 1000 seemed too long... so I decided to name my series of writings "Worth half a picture."

There's no way I can write 500 words every day (certainly not on topics that are interesting to anyone), so these will be a weekly effort. Let's see where it goes.